This invention relates generally to memory cards and, more particularly, is directed to a memory card for use as a credit card and/or identification card having an integrated circuit incorporated therein.
A memory card for use as a credit card and/or identification (ID) card has been proposed having a CMOS integrated circuit (IC) incorporated therein. The IC may include a central processing unit (CPU), a read only memory (ROM) for storing a program and personal data, and a random access memory (RAM) for providing a memory work area. The terminals of the IC are respectively connected to connection terminals formed on an exposed surface of the card. In this regard, during operation, the memory card is inserted into a card reader such that respective contacts of the card reader contact the aforementioned connection terminals to supply a drive voltage and control signals to the IC so that appropriate data stored therein is read out and supplied to the card reader.
However, as previously discussed, the aforementioned connection terminals of the memory card are exposed on the surface thereof, whereby static electricity generated from a human body or clothes, particularly clothes made from chemical fibers and the like, flow through the connection terminals to the IC to damage or destroy the latter. It is to be noted that, while the CMOS IC can withstand approximately 200 volts, static electricity may sometimes reach several thousand volts. Accordingly, known memory cards can not be carried in pockets of clothes made of chemical fibers or the like.
In order to avoid such damage to the IC, resistors having large resistance values, for example, 20K.OMEGA. to 30K.OMEGA. or more, are generally connected in series between various connection terminals and the IC to prevent the IC from being destroyed by static electricity. However, with respect to the power source connection terminal connected to the IC, a resistor having a resistance value of several ten K.OMEGA. cannot be connected in series therewith since a drive current of approximately 1 mA flows therethrough during energization of the IC. Accordingly, if no resistor or a resistor having a small resistance value is connected in series between the power source connection terminal and the IC, the IC is still damaged or destroyed by static electricity through the power source terminal. In addition, for the other connection terminals, it is to be noted that, although the resistors connected in series therewith having large resistance values can protect the IC against static electricity, if the resistance values of these resistors are increased too much, the time constant determined by such resistor and the input capacitance of the IC tend to cause the waveforms of the respective signals to be blunted and to be delayed.